The present invention relates to a process and apparatus for the regeneration of a soot-particle filter located in the exhaust-gas line of an air-compression internal-combustion engine, and more particularly, to a process and apparatus used in a fuel-injected engine wherein, after each transition into the deceleration mode of the engine a cross-section of the engine air intake line is reduced to a minimum and thereafter continuously to a full open position.
It is known from European Patent Specification No. 10,384 to raise the exhaust-gas temperature for the regeneration phase of a soot-particle filter by throttling the stream of intake air. The control used for this ensures, among other things, that the throttle flap or the throttle-flap system is shifted into the opening position at very high temperatures of the soot-particle filter body. When the internal-combustion engine is running in a high load range, i.e., in a range in which high exhaust-gas temperatures are already high, and a regeneration phase is still just taking place, then there is such a high soot-particle filter body temperature due also to the exothermal soot-particle oxidation that the throttle flap is kept in the opening position via the control.
Now, if the internal-combustion engine ie suddenly shifted into a deceleration mode, i.e., no load or virtually no load, there will be an excessive supply of oxygen in the exhaust gas. As a result, the melting temperature of the material of the soot-particle filter body can be exceeded at least in places because of the high exothermy of the reaction of the soot particles with the abundant oxygen, and damage to the soot filter can occur.
An object of the present invention is, therefore, to provide a process for the regeneration of a soot-particle filter in which damage to the soot-particle filter body during transition into the deceleration mode of the internal-combustion engine, especially after a transition from higher load ranges, can be prevented.
In accordance with the present invention, the foregoing object is achieved by providing control of the cross-section of the air intake line from its open position to a minimum opening and thereafter continuously into its open position.
The process according to the invention ensures that, immediately after a transition of the internal-combustion engine into a deceleration mode, the oxygen supply in the exhaust gas is limited. This prevents an explosion-like conversion of the soot particles and consequently a thermal overloading of the soot-particle filter body. To guarantee that soot-particle filter regeneration already taking place is nevertheless supplied with sufficient oxygen, however, the device for controlling the cross-section of the intake line, after it has reached the position reducing the intake-line cross-section to a minimum, is slowly returned to the opening position again.
An impairment of driving capability and too great a reduction of the air-ratio coefficient as a result of an abrupt preset load during this return phase is prevented by the process of the present invention. Furthermore, an advantage of this process is that the internal-combustion engine will not stop as a result of engine speed decrease during the time when the device for controlling the stream of intake air is not in the open position.
These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the process and an apparatus for carrying out that process when taken in conjunction with the accompanying drawings.